An X-ray has high material transparency, and can achieve imaging with high spatial resolution. For these reasons, the X-ray is used for a nondestructive inspection of an object as industrial utilization, X-raying as medical utilization, and the like.
That is, by the X-ray in the above utilization, a contrast image is formed by using a difference of absorption in a case where the X-ray transmits through an object or a living body, due to constituent elements and density differences of the object or the living body. It should be noted that such a process is called an X-ray absorption contrast method.
However, since an X-ray absorption capability of a light element is very small, it is difficult by the X-ray absorption contrast method to take an image of living soft tissue which consists of carbon, hydrogen, oxygen and the like being constituent elements of the living body, or a soft material.
On the other hand, in order to provide a method which can clearly take an image of even tissue consisting of light elements, a research for a phase contrast method using a phase difference of X-rays has been performed since 1990's.
Among numerous phase contrast methods developed, a method capable of obtaining an image by a single X-ray imaging is desirable for somatoscopy, and particularly for medical somatoscopy. For example, a method described in PTL 1 and a method described in NPL 1 have been proposed.
More specifically, in the method described in PTL 1, an X-ray is divided by periodically arranged slits so that the divided X-ray corresponds to a pixel of a detector. Further, an X-ray shielding mask is arranged at the edge of the pixel of the detector, and slight deviation in an X-ray direction which arises when the X-ray transmits through an object to be detected is detected as an output change of the pixel, whereby a phase image is obtained from a first imaging.
Further, in a Scanning Double Grating method (hereinafter, called an SDG method) in NPL 1, imaging is performed while a diffraction grating which forms a self-image and an absorption grating which is disposed at the position of the self-image are simultaneously scanned in the same direction. Thus, an inclination of wavefront of an X-ray is detected as an intensity change through a single imaging, whereby a phase image is obtained.